//禁用退格后退功能
$(document).keydown(function(e){
		var doPrevent;
		if (e.keyCode == 8){
			var d = e.srcElement || e.target;
			if(d.tagName.toUpperCase() == "INPUT"|| d.tagName.toUpperCase() == "TEXTAREA"){
				doPrevent = d.readOnly || d.disabled;
			}else{
				doPrevent = true;
			}
		}else{
			doPrevent = false; 
		}
		if (doPrevent){
			e.preventDefault();
		}
}); 